High Surf in Hawaii, July 26 to 27, 2020

Area Forecast Discussion
National Weather Service Honolulu HI
511 AM HST Sun Jul 26 2020

.SYNOPSIS...
Hurricane Douglas continues to close in on the main Hawaiian
Islands this Sunday morning, carrying with it some dangerous and
potentially damaging weather. The current track of Hurricane
Douglas takes it north of the Big Island later this morning, then
glance the following islands, Maui Sunday at midday, Molokai in
the afternoon, Oahu in the evening, lastly Kauai late tonight and
Monday morning. Once Douglas leaves the area, safely by Monday
night, high pressure to our north will bring back a typical trade
wind weather pattern.

&&

.DISCUSSION...
Condition will continue to worsen across parts of the Big Island
and Maui in the next few hours as Hurricane Douglas near these
islands. After Maui County and the Big Island, Oahu will start
feeling the effects of Douglas this afternoon and this evening,
followed by Kauai late tonight and early Monday morning. There is
little change in the forecast track, which passes just north of
the Big Island shortly after sunrise, and Maui later this morning,
then near or moving over the rest of the main Hawaiian Islands
through the rest of today and tonight. Heavy rains with potential
flash flooding, strong, damaging, and shifting winds will
accompany Douglas. A Flash Flood Watch is currently in effect for
all Hawaiian Islands through Monday. For all other watches,
warnings and potential impacts from Hurricane Douglas, please
refer to the latest Hurricane Local Statement (HLSHFO).

The winds have shifted to the north and northeast across the Big
Island and Maui this morning, ahead of Douglas, which at this
component, favors acceleration through valleys and ridges. The
winds may shift to the northwest and west across Maui and part of
the Big Island later this morning, before shifting to the east and
southeast by tonight for these two islands.

Once Douglas moves west of the main Hawaiian islands, a typical
trade wind weather pattern is expected to return thanks to high
pressure north of the area. Clouds and passing showers will favor
windward and mauka areas.

&&

.AVIATION...
High pressure will remain far north of the islands while
Hurricane Douglas continues to approach the Big Island and Maui
County. Impacts from Douglas will then spread west to the
remaining islands throughout the day. As Douglas moves closer to
the islands, expect an increase in winds as well as MVFR CIG and
VIS in clouds and rain. Occasional IFR VIS/CIGS will be possible
at some sites. AIRMETs for IFR or mountain obscuration and
conditions are likely as are AIRMETs for strong and gusty surface
winds/turbulence.

&&
.MARINE...
All marine interests in the Hawaiian Islands need to complete
any last minute preparations for the arrival of dangerous
Hurricane Douglas this morning. This is a very large hurricane,
so the key message is: Do NOT focus on a small dot representing
the center. Winds of tropical storm force or greater will begin
impacting the waters east of the Big Island and Maui in a few
hours. As of 5 AM HST, the Hurricane Warning is now in effect for
all Hawaiian Waters, except the Leeward and Southeast Big Island
Waters. A Tropical Storm Warning remains in effect for the Leeward
Big Island Waters. See the latest advisory from the Central
Pacific Hurricane Center in Honolulu for additional information
on Douglas.

Seas will remain near the Small Craft Advisory (SCA) threshold
across portions of the Southeast Big Island due to swells from
Hurricane Douglas. Therefore, the SCA is in effect through this
afternoon.

The very large swell from Hurricane Douglas has arrived along
east facing shores of the Big Island and Maui County, and will
continue to build there, and then spread to Oahu and Kauai
today and tonight. Very large and dangerous surf is expected, so
a High Surf Warning (HSW) is in effect for east facing shores of
most Hawaiian Islands. Hazardous surf is also possible along the
north facing shores of islands that are exposed to the large east
swell and strong winds. A High Surf Advisory has been issued for
north facing shores of most islands. In addition to the life-
threatening surf, ocean water will likely surge over some parts
of the coastline. This may cause damage to roadways and other
coastal infrastructure, especially during times of high tide.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Hurricane Warning for Niihau-Kauai-Oahu-Molokai-Lanai-Kahoolawe-
Maui.

Tropical Storm Warning for Big Island.

Flash Flood Watch through Monday afternoon for all Hawaiian
Islands.

High Surf Advisory from 6 PM this evening to 6 PM HST Monday for
Kauai Leeward-Oahu North Shore.

High Surf Advisory until 6 AM HST Monday for Molokai Leeward-
Maui Central Valley.

High Surf Warning until 6 AM HST Monday for Molokai Windward-
Kahoolawe-Maui Windward West-Windward Haleakala-Leeward
Haleakala-South Big Island-Big Island North and East.

High Surf Warning until 6 PM HST Monday for Kauai Windward-Oahu
Koolau-Olomana.

Hurricane Warning for Kauai Northwest Waters-Kauai Windward
Waters-Kauai Leeward Waters-Kauai Channel-Oahu Windward Waters-
Oahu Leeward Waters-Kaiwi Channel-Maui County Windward Waters-
Maui County Leeward Waters-Maalaea Bay-Pailolo Channel-
Alenuihaha Channel-Big Island Windward Waters.

Tropical Storm Warning for Big Island Leeward Waters.

Small Craft Advisory until 4 PM HST this afternoon for Big
Island Southeast Waters.

&&

DISCUSSION...H Lau
AVIATION...Schneider (NWS Monterey, CA)
MARINE...Houston